The present invention relates to a control method and system for engine valve actuation.
In U.S. Pat. No. 6,009,841, an engine with a hybrid valvetrain is disclosed in which one intake valve is actuated by a source other than a camshaft. This first intake valve is randomly operable meaning that the valve opening and closing events are, independent of engine crankshaft position, thus, a fully variable valve. A second intake valve is actuated by a camshaft and includes a deactivator. Operation of the second valve may be discontinued or restored within one engine cycle, termed selectable intake valve herein. The exhaust valve(s) of the hybrid valvetrain is conventionally camshaft actuated.
In U.S. Pat. No. 6,009,841, the method is described in which air is admitted using a randomly operable intake valve when the engine is operating in a lowest range in torque, using a selectable intake valve when the engine is operating in a medium range in torque, and using both the randomly operable intake valve and the selectable intake valve when the engine is operating in a highest range in torque.
In U.S. Pat. No. 5,669,341, a method is described in which air is admitted through a smaller randomly operable intake valve when the engine is operating in a lowest range in engine speed, through a larger randomly operable intake valve when the engine is operating in a medium range in engine speed, and through both randomly operable intake valves when the engine is operating in a highest range in engine speed.
In U.S. Pat. No. 5,647,312, a method is described in which air is admitted using a randomly operable intake valve when the engine is operating in a lower range in torque and speed and air is admitted using a selectable intake valve when the engine is operating at higher speed or higher torque. The determination of which valves to actuate is based on predetermined rpm and engine torque levels.
The inventors herein have recognized that U.S. Pat. Nos. 5,647,312, 5,669,341, and 6,009,841 do not disclose a method by which transitions among the various operating modes can be accomplished.
The object of the present invention is to control trapped fresh charge in an internal combustion engine during transitions between operating modes.
The above object is achieved by a method for controlling an internal combustion engine intake air flow during a transition, with the engine having at least one cylinder, at least one randomly operable intake valve, at least one selectable intake valve, and a throttle valve disposed in the intake manifold. In the method demanded engine torque is sensed from which desired manifold pressure trajectory can be computed. The throttle valve position and the closing time of the randomly operable intake valve are adjusted based on the manifold pressure trajectory.
The advantage of the present invention is that by adjusting the throttle valve position and the closing time of the randomly operable intake valve based on desired manifold pressure trajectory transitions among operating modes of the selectable and randomly operable intake valves, transitions can be accomplished smoothly, that is, without perceptible torque fluctuation.
Other advantages, as well as objects and features of the present invention, will become apparent to the reader of this specification.